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Atlantic and Caribbean: Lionfish Invasion Threatens Reefs

Lionfish on a coral reef in The Bahamas. Photo credit: Richard Carey, www.richardcareyphotos.com.

Recent news reports from Texas to Jamaica to the Bahamas have documented the rapid spread of the lionfish—an invasive marine species. Lionfish have quickly become established across the waters of the southeastern U.S. and the Caribbean. New sightings abound—earlier this month lionfish reached the Flower Garden Banks National Marine Sanctuary off the coasts of Texas and Louisiana. Because of their role in upsetting the ecological balance of coral reef ecosystems, the rapid growth in the populations of these fish poses a grave threat to the region’s coral reefs. Consequently, the region’s fishing and tourism industries, which depend on coral reefs, may also be at risk. Governments across the region are trying to respond to the lionfish invasion by developing new campaigns and cooperation strategies that could pose important lessons for how to deal with invasive marine species in the future.

Two species of lionfish (Pterois volitans and P. miles) are responsible for this recent and growing threat to Atlantic and Caribbean reefs. Native to the Indo-Pacific, these species’ colorful and dramatic appearance make them popular ornamental fishes in saltwater aquariums (see photo above). Though no one is certain how or when the lionfish invasion began, strong evidence suggests that people first introduced lionfish to the Atlantic along the southeastern coast of Florida, where they were first sighted in 1985. By 2001, people reported sightings in waters off the coasts of Georgia, the Carolinas, and Bermuda. Over the last decade, lionfish population densities have increased in these areas and these species have spread southward, and are now established throughout much of the Caribbean (see slideshow below). Lionfish are now invading the Gulf of Mexico and the northern coast of South America. These fish pose a serious threat to reef fish populations across the region, and thus to coral reef ecosystems and the people who depend on them.

With venomous spines, lionfish have few natural predators in their native habitat, and no native predators in the Atlantic and Caribbean region.

Lionfish are also voracious hunters, known to consume more than 50 other species of fish in the region.

Lionfish multiply quickly; a single female spawns more than 2 million eggs per year.

Finally, they can live in multiple coastal habitats, including coral reefs and mangroves, and at depths ranging from close to shore to more than 300 meters.

In the Caribbean, more than 75 percent of coral reefs are already threatened by a combination of overfishing, pollution from land and sea, and coastal development. Overfishing, the most pervasive threat to Caribbean reefs, has already devastated populations of many large predators such as groupers and snappers. On some reefs even herbivorous fish populations have been greatly reduced. As populations of herbivorous fish have declined, the health of coral reefs has been negatively impacted by the growth of algae on the reefs. Other threats, including disease, hurricanes and coral bleaching, further add to the pressure on the region’s coral reefs. An unchecked lionfish invasion, on top of these threats, could possibly lead to irreversible changes to Caribbean reef ecosystems, including further reductions in forage (prey) fish species, competition with predator fish species, and increased algal growth and degradation of reefs due to the reduction in herbivorous fish.

Governments across the region are developing lionfish management plans, hoping to bring lionfish populations back to a level where they no longer impact other fisheries.

Some governments (such as the U.S. and Jamaica) are initiating campaigns to promote human consumption of lionfish, training fishermen how to safely catch, handle, clean and prepare them. Public education campaigns are helping to promote lionfish consumption and develop a viable market.

Other management efforts have focused on training divers to capture lionfish, and hosting derby-style events where divers remove large numbers of lionfish from protected areas.

Governments are also conducting monitoring of lionfish populations and population growth patterns, as well as sponsoring research of preferred lionfish prey species and possible predator species (such as grouper).

Efforts are also underway to coordinate a region-wide response to the invasion, including sharing of “best lionfish management practices” among coral reef managers, collaboration between national governments, and partnerships with the fishing and tourism industries, civil society and research institutions.

Going forward, it will be critical to learn as much as possible from the lionfish invasion to prevent future invasions before they reach such critical levels. Early detection and rapid response programs, increased awareness of invasive species and their impacts, species risk assessments and increased regulation of the aquarium trade could all help reduce the risk of future invasions in the marine environment.